This invention generally relates to electrical power disconnect switches and, more particularly, to a very compact disconnect switch which has a very broad current rating.
Present commercial switches specially designed for use with voltages less than about 5,000 volts and very high currents have traditionally been of the knife blade type which has a moving conductor hinged to open and close into a stationary contact. The problem with this design is that at very high current ratings, the moving conductor gets so large that it dictates an excessively large open gap for the low voltage rating. The low voltage open gap required to provide adequate electrical open clearance may be only one inch, but a knife blade conductor large enough to carry a typical 5,000 amp. load could not physically pivot on a hinge and be only one inch long. For these reasons, knife blade switches have traditionally been inefficient at such ratings because of blade length.
To avoid hinging the moving element of the switch, switches which utilize a "bridge" member have been used wherein a wedge-shaped bridge is forced into contact between two similarly shaped bus conductors. The bridge in such a switch makes a butt contact which has certain disadvantages.
Disconnect switches for use with higher voltages and used outdoors where ice breaking is essential have utilized reverse-loop contact members with a conductor member rotated against the contact members to provide a wiping contact opening action. Such switches have then moved the rotated contact member away from the loop contact members. Such a switch uses compression springs with the reverse-loop contact members. This construction is generally described in U.S. Pat. No. 4,339,636 dated July 13, 1982, to C. M. Cleaveland et al. A modified type of such a switch is shown in U.S. Pat. No. 4,379,956 dated Apr. 12, 1983, to C. M. Cleaveland et al. wherein an insulated spring connecting between two reverse-loop contact members provides the necessary contact tension. Again, such a device is normally used for higher voltage outdoor switch applications and after the circuit is opened, the rotatable contact member is pivoted away from the reverse-loop contact portions.